I think interactive features aren't used more often because there tends to be significant programming work required to make them. The "explorable explanations" movement has produced amazing works (e.g. http://ncase.me), but there's a lot of custom code involved.
Some aspects of interactivity can be handled by a one-size-fits-all solution (like zoomable charts or embedded video/audio), but I don't think that it will be possible to go much further without involving programmers. And that makes interactive features orders of magnitude more expensive than just a static image, leaving the cool stuff to hobbyists who have the time to make it work.
I know there are specialist JavaScript libraries for this, but I find it hard to believe that there aren’t any WYSIWYG tools that allows you to create layouts and add interactivity such as hotspots and simple animation..
Some aspects of interactivity can be handled by a one-size-fits-all solution (like zoomable charts or embedded video/audio), but I don't think that it will be possible to go much further without involving programmers. And that makes interactive features orders of magnitude more expensive than just a static image, leaving the cool stuff to hobbyists who have the time to make it work.